licht.wissen No. 01 "Lighting with Artificial Light"

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licht.wissen 01 Lighting with Artificial Light 77 Luminaires and their power supply units Any discussion about “energy-efficient lighting” or “visual ergonomics” also includes electronic power supply units: in combination with economical light sources they form an energy-saving duo. Modern, energy-efficient lighting technologies require power supply units. They cannot simply be connected to the mains like high-voltage incandescent and halogen lamps. The exceptions here are retrofit lamps with built-in power supply units (CFLi, LED retrofit). External power supply units are often built into the luminaire or incorporated in the electrical circuit. Electronic ballasts (EBs) Where possible, traditional light sources are operated with electronic ballasts. This is because, besides energy efficiency, they also offer many other lighting quality benefits, such as such as flicker-free light as the result of their high-frequency operation. Depending on the type of the electronic ballast, the light sources can also be controlled or dimmed. However, or highwattage high-pressure discharge lamps > 400 Watts there are currently scarcely any reliable electronic devices. The service life is of importance here: conventional ballasts are very robust and virtually “unbreakable”. The quality of the components used in electronic ballasts, by contrast, has a significant impact on their service life. LED module components LED modules can be voltage or current controlled; components with power supply functions may be pre-installed on the module circuit board. The smarter the design of the control or driver system is with its relevant interfaces, the more adaptable it will be to the actual lighting requirements: colour control and dimming can be used to simulate daylight during the day and thus are ideal for providing health-oriented light. What are power supply units needed for? Light sources have different current requirements: different lamp types such as lowvoltage halogen lamps need transformers. They reduce the mains voltage of 220- 240 V 50 Hz alternating current (AC) to 6, 10, 12, 24, 42 V or, in rare cases, also other safety extra-low voltages. LEDs also need transformers; in this case also with rectifier function, because LEDs need to be supplied with direct current (DC). Currentcontrolled LED modules need units which 40
78 supply constant output currents such as 350 mA, 700 MA or 1,050 mA. Discharge lamps cannot be connected directly to the mains, either. They need a start pulse – either from an external igniter (in fluorescent lamps: starter) or from a builtin igniter or ignition mechanism. Even if the ignition were to succeed, the current strength would theoretically rise to infinity (with a relatively constant mains voltage due to the negative current/voltage characteristic of discharge lamps). In practice this means that the lamp would be destroyed at some point. Accordingly, ballasts also serve to limit the current and are therefore vital for operation of the lamp. An electronic ballast (EB) combines a ballast and ignition mechanism in a single device. It works with high-frequency alternating voltage of 25 to 40 kHz which, in fluorescent lamps, leads to a significant reduction in power consumption, yet delivers the same luminous flux. In conventional operation, the system power consumption of a 58 W lamp + conventional ballast power loss is approx. 7-10 W = 65 – 68 W; = in electronic ballast operation, however, 50 W lamp + approx. 5 W electronic ballast power loss = 55 W, representing a saving of about 23 per cent. Lighting management – Power supply unit requirements Lighting management systems control or regulate brightness, and sometimes also the light colour of a lighting system. The requirements essentially concern dimming: pure brightness control means allowing a light source of one colour to emit more or less light. This is simple in the case of incandescent lamps: less current heats the filament to a lesser degree, making it emit less light. Side effect: the light colour becomes warmer. In LEDs and discharge lamps this only changes slightly or not at all during dimming. Colour changes can only be obtained by mixing light sources of different light colours (LED chips, coloured fluorescent lamps) in different states of dimming. Some light sources such as metal halide lamps cannot be readily regulated and can only be dimmed under certain conditions and with a minor adverse colour shift towards green, whereas other light sources such as LEDs or fluorescent lamps are easily controllable. But not all power supply units support the dimming of light sources. Conventional power supply units can only be switched in steps, such as night-time street lighting in which the lamp can be switched to 50 per cent power after a warm-up phase of at least 15 minutes. Not all electronic ballasts meet this requirement: dimmable or smart electronic ballasts are required for this. Additional colour control for LEDs requires either an extra control unit or a suitable driver with the appropriate number of outputs. The interfaces of the power supply units should be selected depending on the type of signal, i.e. the lighting control method. 1 – 10 V control technology is sufficient for simple dimming. DALI (Digital Addressable Lighting Interface) systems can be used to control rooms and buildings. DMX (multiplex transmission) which, like DALI, can be integrated into overall building system control systems such as KNX, is suitable for larger solutions. Each power supply unit must be able to communicate with the control components and be configured accordingly. [77 + 78] Indoor or outdoor: Modern luminaires work with electronic power supply units. They regulate the power supply and ensure efficient operation. 41
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licht.wissen No. 01 "Lighting with Artificial Light"

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